Crustal evolution in the central part of Eastern NCC: Zircon U−Pb ages from multiple magmatic pulses in the Luxi area and implications for gold mineralization

Abstract

The Luxi area in the central part of Eastern North China Craton (NCC) is located in a relatively stable intraplate environment and preserves some of the large granite–greenstone belts in the North China Craton (NCC). The intensity and extent of multiple magmatic pluses associated with the destruction of the NCC during Mesozoic were comparatively less in this region. However, the nature and timing of the magmatic pulses in the Luxi area are critical to the evaluation of the differential destruction of the NCC's lithosphere as well as in understanding the origin and extent of the associated gold mineralization.In this study, we report new zircon U−Pb data on the basement rocks in the Luxi area which show that the protoliths of the TTG (tonalite–trondhjemite–granodiorite) gneisses, granitoids and amphibolites formed at 2572.2±8.8Ma, 2531±12Ma, and 2572±32Ma respectively. The Luxi area experienced two major crust accretions at 2.7−2.75Ga and ca. 2.5Ga. The Mesozoic Tongshi complex formed at 175.6±1.7−178.4±2.1Ma associated with fluid modification at the later stage of magma crystallization. The alteration age (162.2±3.2−165.4±2.8Ma) may represent the mineralization age of the Guilaizhuang gold deposit. The diorite porphyry of Tongjing complex was emplaced at 128.0±5.4Ma. The inherited zircon and Lu−Hf isotope data suggest extensive recycling of basement rocks in the Luxi area. The sequence of Mesozoic magmatic intrusions shows a clear variation from intermediate (alkaline) through intermediate (cal-alkaline), and felsic–mafic, and the main intrusive ages can be divided into distinct phases at 170–200Ma, 100–150Ma (with peak at 120–130Ma), and 80–90Ma respectively. The Tongshi complex formed during the compression–extension stage after the collision of the Yangtze Craton and North China Craton, whereas the Tongjing complex and other alkaline, felsic and mafic complexes in the Luxi area formed within the geodynamic setting of Pacific subduction. The early Cretaceous magmatism also simultaneously occurred in the Taihang Mountain area (far from the plate margin) in the central part of the North China Craton, with related gold mineralization. The Mesozoic gold mineralization in Jiaodong and Luxi in the eastern, and those in the central parts of the North China Craton appear to be linked to extensive crustal recycling in an extensional tectonic regime.